In FY 2010, we continued investigation of the staphylococcal peptide cytolysins, phenol-soluble modulins (PSMs). In collaboration with Dr. Andreas Peschels group from the University of Tubingen, Germany, we discovered and investigated PSMs in multiple staphylococcal pathogens. Furthermore, we found that proteolytically processed PSMs of S. aureus have antimicrobial activity, predominantly against Streptococcus pyogenes, suggesting intra-species competition via PSM activity. Current efforts focus on structure-function relationship studies of PSMs and the identification of the PSM exporter, with the long-term goals to produce anti-PSM therapeutics for the treatment of staphylococcal infections. Furthermore, we continued our efforts to elucidate the basis of virulence in community-associated MRSA. We characterized the role of the accessory gene regulator in CA-MRSA and, in collaboration with Dr. Li (Shanghai), we analyzed virulence and virulence factor production in a series of global CA-MRSA strains. Further work on CA-MRSA is being conducted in close collaboration with Dr. DeLeos group at RML, Dr. Diep at UCSF, and Dr. Li at Fudan University. Finally, we collaborated with Dr. Smeltzer to elucidate the role of the sarA regulator in S. aureus.